Use direct client flow control instead of prefetch_count (bug 26619)

The hard coded prefetch count we had was a bit low, but we were only
using it for flow control anyway, so let's use the more lightweight
flow control mechanism we have now.

deps/rabbitmq_tracing/src/rabbit_tracing_consumer.erl

@@ -57,11 +57,10 @@ init(Args) ->
     amqp_channel:call(
       Ch, #'queue.bind'{exchange = ?X, queue = Q,
                         routing_key = pget(pattern, Args)}),
-    #'basic.qos_ok'{} =
-        amqp_channel:call(Ch, #'basic.qos'{prefetch_count = 10}),
+    amqp_channel:enable_delivery_flow_control(Ch),
     #'basic.consume_ok'{} =
         amqp_channel:subscribe(Ch, #'basic.consume'{queue  = Q,
-                                                    no_ack = false}, self()),
+                                                    no_ack = true}, self()),
     {ok, Dir} = application:get_env(directory),
     Filename = Dir ++ "/" ++ binary_to_list(Name) ++ ".log",
     case filelib:ensure_dir(Filename) of
@@ -94,11 +93,11 @@ handle_call(_Req, _From, State) ->
 handle_cast(_C, State) ->
     {noreply, State}.
 
-handle_info(Delivery = {#'basic.deliver'{delivery_tag = Seq}, #amqp_msg{}},
+handle_info({BasicDeliver, Msg, DeliveryCtx},
             State    = #state{ch = Ch, file = F, format = Format}) ->
+    amqp_channel:notify_received(DeliveryCtx),
     Print = fun(Fmt, Args) -> io:format(F, Fmt, Args) end,
-    log(Format, Print, delivery_to_log_record(Delivery)),
-    amqp_channel:cast(Ch, #'basic.ack'{delivery_tag = Seq}),
+    log(Format, Print, delivery_to_log_record({BasicDeliver, Msg})),
     {noreply, State};
 
 handle_info(_I, State) ->